In closed greenhouses, the irrigation water is known to be enriched with carbon dioxide gas to enhance both the growth and resistance of the plants to diseases and pests by influencing the quality of the soil. One of the known irrigation systems may be employed for introducing the water impregnated with carbon dioxide into the soil, such as, for example, the drip irrigation system, the channel irrigation system, the catchment type irrigation system and the rain gun type irrigation system. For the introduction of the water enriched with CO.sub.2 into the soil, it is essential that the absorptivity for CO.sub.2 in water should be increased above the normal absorbing capacity and that a fine impregnation should be achieved, which prevents free bubbles in the irrigation water from impairing or blocking the supply-, dosing-and nozzle systems or the like.
Owing to the high degree of impregnation, the spraying or aerosolizing of the so high and fine impregnated irrigation water results in losses in CO.sub.2 already upon the discharge of the irrigation water and consequently, renders these types of irrigation system less economical.
On the other hand, the spraying of irrigation water has gained importance for so-called leaf dressing or fertilizing. In leaf dressing, one utilizes the capability of the plants to directly take up nutrients through the leaves and sprays nutrient solutions, to which fungicides or other pesticides may be also added, directly on the plants leaves. In doing so, difficulties often arise due to the fact that the fine supply and nozzle areas of the nozzle system are impaired or clogged by deposits of the dissolved nutrients, herbicides or pesticides. Hence, these systems require continuous maintenance and cleaning. Another disadvantage is to be seen in the deposits and spots formed on the plant surface. Moreover, when this system is used, the substances are to be converted to a compound, for example, a chelate, adapted to be better taken up by the plants, a fact that makes the method more expensive and impedes its large scale employment.